1. Field of the Invention
The present invention relates generally to wireless communication systems, and more specifically, but not exclusively, to a method and apparatus for signaling physical layer information in a broadcast system.
2. Description of the Related Art
A wireless communication system, such as a Digital Video Broadcasting (DVB) system, transmits data in a sequence of frames. For example, a DVB system may operate according to a DVB-Terrestrial 2nd Generation (T2) standard, an Advanced Televisions Systems Committee (ATSC) standard, an Integrated Services Digital Broadcasting (ISDB) standard, or a Digital multimedia Broadcasting (DMB) standard. Each frame typically includes a preamble section and a data section, which are time-multiplexed. The data section carries data arranged in a number of data streams, which are commonly referred to as Physical Layer Pipes (PLPs). For example, a PLP may carry a service, such as a video channel provided to a user.
Reception of data from the frames, and reception of the data streams, may be assisted by signaling, which is typically carried in the preamble of the frame, i.e., Out-of-Band (OB) signaling, and/or carried in the data section, typically of the preceding frame, i.e., In-Band (TB) signaling. The signaling may be referred to as physical layer signaling, or Layer 1 (L1) signaling. The signaling may indicate a modulation or coding scheme to be used for decoding data, and sections of a data field to be decoded, or the location of a data stream within the data section.
The efficiency of L1 signaling, in particular, for battery-powered digital broadcasting receivers in a mobile environment, may be measured mainly from the perspectives of Robustness, Power Consumption, delay in changing channels (“zapping” delay), and Latency. Prior art systems in the mobile broadcasting context may suffer from insufficient robustness of L1 signaling as compared to robustness of data. This is quite critical as the L1 signaling is important to access the data later in the frame. Accordingly, if the L1 signaling is lost, the data will be lost too. The lack of robustness is mainly due to the lack of time diversity as the L1 signaling, in particular, OB signaling, may be located at the beginning of a frame and typically does not apply any time interleaving across the frame.
In order to alleviate this problem, some solutions have been proposed and adopted as options in the context of the DVB-T2 standard. Specifically, a repetition solution repeats the L1 signaling corresponding to a next frame, in a current frame. Thus, the L1 signaling has two copies, one in the previous frame and another one in the current desired frame, which improves the robustness at the expense of doubling the overhead, i.e., reducing the spectral efficiency.
Additionally, IB signaling has been proposed, which involves encapsulating the L1 signaling for accessing and decoding data at a following frame into a data section of a current frame. In this proposal, the signaling is time interleaved and benefits from a higher diversity. However, the IB signaling is applicable for continuous reception only, but not for initial scanning, zapping, or updating. IB signaling may provide some improved service continuity at good robustness, but still not enough, or in low mobility scenarios.
Specifically, conventional systems do not provide an efficient L1 signaling solution that achieves robustness for initial scanning, service continuity, zapping, and updating, and is applicable in a variety of mobility scenarios.